Jan to Feb at WDW regular rates are $125 to $170 per round depending on course. The DVC golf card costs about $91 with tax and is good for a year. Only the member can get that card and he can go and bring 3 guests who will also get the discounted rate of $95 a round. The member must be there as he is the only one who can use the DVC golf card. In other words you must be there and pay $95 for your round for any guest to have the same privilege. The discount can be used for rounds only after 10 a.m.
From end of April through Sep, the discount rate is $35 per round and same rules apply. Note, at that time of the year the regular rate after 10 a.m. for a round is only from $45 to $60 and thus the percentage of discount can actually be lower than during peak season. Oct to Jan the discount rate for rounds after 10 has been $50, while regular rates after 10 at that time were $70 to $110.
Because of the $91 cost for the DVC golf card, you need to have enough rounds in a year's time so that you get a true discount, e.g., if you only play one round per year, getting the DVC golf card is useless because the discount for the round does not make up for the cost of the card.
As to HH and VB, there are designated courses at which a DVC member can get a discount (usually in the 10% to 15% range depending on course). For those, you do not need to buy any discount card; they are just straight discounts. But the discounts are only available to the member (and for some courses guests that the member brings with him).